Mattresses of resilient foam material have long been popular owing to their low weight and cost. However, they are generally too soft to provide the support required by many people, especially those with back ailments. If the mattress is made thin in an attempt to reduce the extent of the depression induced by body weight, protruding portions of the sleeper's body, such as the hip bone and elbows, compress the mattress to maximum density and provide an uncomfortable sleep.
Another problem encountered in mattresses generally, not only of the resilient foam type but also the spring variety, is the tendency of the large sag or depression caused by a heavy person to extend to the adjacent portion of the mattress. Should a lighter person also be sleeping on the mattress, the large depression caused by the heavy person tends to make the lighter person roll down the side of the depression. Under such circumstances the lighter person is unable to enjoy a restful sleep.
The prior art is not lacking in disclosures of various types of mattresses endeavoring to overcome the foregoing problems.
Some of the prior art patents have in fact suggested that inserts be interposed between layers of mattresses (such as my U.S. Pat. No. 3,818,519 in which a basket-weave matrix of flat strips is used) to alleviate the problems.
Other have utilized sheets of plywood, particle board, or the like, horizontally sandwiched between layers of foam material, exemplary being I. Young et al U.S. Pat. No. 2,543,218 and S. Lerman U.S. Pat. No. 3,323,152. Such devices minimize sag but lack the comfort afforded by more flexible inserts.
Still others, such as R. R. Upton U.S. Pat. No. 3,319,274, prefer thin corrugated metal sheets inserted between foam layers, with the corrugation channels longitudinally aligned with the long dimension of the mattress. Such mattress construction will not sag appreciably in a longitudinal direction and it also permits the mattress to be rolled up transversely into a compact roll. By the same token, however, the problem of the sag induced by a heavy person and the effect upon an adjacent sleeper is not solved by the corrugated metal insert disclosed in Upton.